I don't know what was so hard to just include an option of having them die in the first place.
It was optional in NV too.
It's a really stuffty feeling to know that if I can't handle a certain area I can just let my unkillable meat shield with unlimited ammo handle the area for me. I've done it before, in Fallout 3 I didn't feel like dealing with ghouls so I had Charon kill all of them for me.
He's unkillable, unlimited ammo, high ass health, knows where all the enemies are and has an aim bot.
I don't like having that sense of security when I need to get through an area because sometimes I abuse it and I don't want to.